For what it’s worth - I called today to ask about signing up.
I was told that there are 2 visits required, with a third optional visit. The first two visits have to be completed before the end of this year. Given my work schedule and family obligations, I cannot make two trips to the East coast in the next month and a half.
However, the good news is, I was told by the screener that the hospital is receiving the level of respondents they had hoped for. So at least it sounds like this first phase is to be completed soon and that participation is high. At least this is encouraging.